Today, Riina meets Kenji, her mother's new husband, for the first time. Kenji, a company president, lives in a newly built house, and a room has already been prepared for Riina, his new stepdaughter. Gentle and kind, Kenji shows thoughtful concern for Riina, who is busy studying for exams, making it clear he warmly welcomes her as his daughter. However, no one could have imagined that the joking remark her mother made—"No, Kenji... don't lay a hand on my daughter"—would soon become reality. Between the two, an illicit relationship is about to begin.